<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
</head>
<body>
    <div class="one">hello world</div>
    <div class="one">hello world</div>
    <div class="one">hello world</div>
    <script>
        /* 通过class获取的是HTMLCollection,html的集合，它长得像数组
        length 获取集合的长度
        可以通过下标去读取 */
        var one=document.getElementsByClassName("one");
        console.log(one)
        console.log(Array.isArray(one))
    </script>
</body>
</html>